The invention relates to a method and a device for monitoring a post print processing machine through which printed products are transported successively, wherein an image recording device that is assigned to the post print processing machine and is connected to a computer unit records with a time interval an image series, comprising at least two images, of a printed product during each operating cycle. The images are then transmitted to the computer unit where the images of the image series are displayed on a display device that is connected to the computer unit.
Processing stations which can process a multitude of printed products per second are used for the processing of printed products. In this connection, the processing speed is frequently specified as number of operating cycles per time unit, for example “number of operating cycles per hour.” A single operating step is generally carried out on a printed product during one operating cycle and/or the printed product is conveyed further by a specific distance during the operating cycle. In the following operating cycle, the next printed product is then subjected to the same operating step and/or the next printed product is conveyed further by the same distance. Owing to the fact that the printed products are flexible products for which the processing quality depends to a high degree on the processing speed, it is a problem in many cases to adjust the operating parameters of the processing stations so as to ensure a problem-free processing of the printed products at a predetermined processing speed and in cases of an increase or reduction in the processing speed. It has proven to be especially problematic in this connection that the sequential processes in the processing stations occur so fast that they can no longer be seen with the human eye. A visual control of the effects on the printed products caused by a change in the operating parameters is thus hardly possible. In addition, existing measuring means such as light barriers, presence check devices and similar sensors cannot be used to determine the quantitative deviation from the ideal operation.
A method and a device for solving these problems are described in the European Patent document EP 1952986 A1, for which initially a light flash is generated which is controlled synchronously with the operating cycle. This light flash creates for the eye of the operator a static image of a moving process in the post print processing operation, which image allows the operator to detect critical production states that cannot be seen with the naked eye and cannot be solved without auxiliary means. During each operating cycle and as a result of the static image generated with the light flash for the observer, the image recording device will simultaneously record an image during each operating cycle of the printed products to be processed. The machine control evaluates the images which respectively show the position of a printed product and then transmits corresponding signals to the adjustment members, provided the process needs to be adjusted.
The German Patent document DE102007058708 A1 also describes a method and a device by means of which certain regions of the printing press are filmed with a video camera and the video films are stored in a storage device or memory. To aid operating personnel during the process of making adjustments and carrying out difficult operations, as well as to analyze and detect error functions, the stored video data can subsequently be transmitted via a data line to an optional control location for the printing press. The recorded processes can thus be viewed again in further detail, e.g. in slow motion, at a later moment.
However, it has turned out that none of the above-described known methods permit a reliable machine adjustment and/or a permanent monitoring of the production processes at high processing speeds.